1. Field of the Invention
The present invention relates to a method for manufacturing a color filter, and more particularly, to a method for manufacturing a color filter of a liquid crystal display (LCD), by a thermal transfer method using a laser beam with modified energy distribution.
2. Description of the Related Art
A conventional color filter has the structure as shown in FIG. 1. The conventional color filter includes black matrix layers 12 on a glass substrate 11, red, blue and green color filter layers 13a, 13b and 13c formed among the black matrix layers 12, and a protective layer 14 and a transparent electrode layer 15 sequentially formed on the black matrix layer 12 and the color filter layers 13a, 13b and 13c.
The color filter is manufactured by a pigment dispersion method, a printing method or an electrodeposition method. According to the pigment dispersion method, the color filter is formed by coating, exposing, developing and sintering a pigment dispersed in a photosensitive resin. The above methods provide excellent accuracy and reproducibility, but manufacturing process is too long and complicated.
The color filter may also be manufactured by a printing method in which red, green and blue inks are coated on a printing board. However, the printing process has poor accuracy and reproducibility.
In the electrodeposition method, red, green and blue color filters are electrochemically formed on transparent electrodes. By this method, the planarity of the color filter is good, but color characteristics, such as purity, are deteriorated. To solve the above problems, a thermal transfer method has recently been proposed. U.S. Pat. Nos. 5,220,348, 5,256,506, 5,278,023 and 5,308,737 discloses a thermal transfer method. According to these disclosures, for the thermal transfer method, at least a light source, a transfer film and a substrate are required. The light emitted from the light source is absorbed by a light absorbent in the transfer film, and converted into heat energy. A material for forming a transfer layer of the transfer film is transferred onto a substrate by the heat energy, thereby resulting in a desired image. Also, U.S. Pat. No. 5,521,035 discloses that the thermal transfer method can be applied to the manufacture of a color filter for a LCD. In the manufacture of a color filter by the conventional methods, a laser beam having a shape like a Gaussian distribution, as shown in FIG. 2, is used as a light source for the transfer of a transfer layer.
U.S. Pat. No. 4,925,523 discloses the use of two or three laser beams having a shape like a Gaussian distribution so as to improve the etching depth and etching efficiency during etching of an organic material by a laser beam. In detail, an organic material is excited by a laser beam having a short wavelength and etched by adopting a laser beam having a long wavelength, wherein the size of two laser beams are similar to each other.
U.S. Pat. No. 5,018,805 discloses a laser printer using a plurality of lasers for a printing process, in which different laser beams are simultaneously irradiated onto different regions, not one region, in order to increase the printing speed.
In the thermal transfer method, the quality of transfer pattern depends on the energy distribution of a laser beam used for the transfer. In the case where a color filter is formed by the thermal transfer method as described above, using a laser having the Gaussian distribution as shown in FIG. 2, the laser generates a Gaussian beam 31 having a predetermined diameter as shown in FIG. 3, to scan an arbitrary color filter pattern 32 in the X direction for thermal transfer. In this way, the intensity of beams becomes weak at the edge of the pattern 32, the quality of image formed on the edge is deteriorated compared to the image formed on the center of the pattern 32. To solve these problems, the entire energy level throughout the pattern 32 can be strengthened, thereby improving the quality of an image at the edge of the pattern 32. However, the energy level becomes excessive at the center of the Gaussian beams, thereby causing unevenness to a surface of the final color filter pattern.